Hydraulic fracturing is a common practice in unconventional oil and gas plays used to efficiently extract hydrocarbons from a formation. One method utilized in stage fracking is thru a series of sleeves with ball seats arranged smallest to largest with the smallest ball seat starting at the end of the well moving upwards in consistent increments. Typically before hydraulic fracturing is allowed to commence integrity of the well is confirmed using a retrievable bridge plug set above all the frac sleeves. After the plug is set and holds a predetermined amount of applied pressure, the plug is released and retrieved to the surface. Hydraulic stage fracturing then commences by dropping a series of balls of increasing diameter so that sleeves are shifted to expose frac ports in a direction from the end of the well towards the surface as incrementally larger balls are dropped. After the fracturing is completed with all the sleeves shifted, the well is put into production.
To speed delivery in some applications the retrievable bridge plug can be deployed and set on electric line with a setting tool that when triggered creates relative movement of a setting sleeve with respect to a tension mandrel acting to compress the sealing elements into contact with the surrounding tubular, generally casing. This action sets the bridge plug by generating sufficient force to packoff the element sealing rubbers thus creating a temporary plug. Typically these plugs have a ratchet locking system to hold the set position and trap setting force in place accomplished during the setting of the tool. After the plug is set, the setting tool features a mechanism that facilitates release of the electric line and adapter kit from the bridge plug. Alternatively the plug can be run in on coiled or jointed tubing depending on the well configuration and the locally available equipment.
To release such plugs the locking mechanism is defeated usually by a tool that breaks a shear pin and moves a sleeve that allows the well to equalize through a bypass featured on the bridge plug. After that happens the sealing element and slips extend axially and retract radially so that the packer or plug can be removed. What has been discovered is that the setting, applied pressure, pressure reversals and releasing process causes parts of the individual packing elements to break up and fall off. This can be devastating to the frac job which relies on a series of balls to seat on ball seats. With a chunk of rubber sitting on a ball seat the deployed balls may actuate the wrong frac sleeve. The debris could also prevent the ball from creating a seal against the ball seat. The debris can also land on one of the ball actuated seats or worst case even the upper most ball actuated seat. If debris lands on one of the frac sleeve ball seats the risk of premature or insufficient actuation is very high.
Debris barriers have been used before with packers to keep debris out of moving parts for packers that remain in a set position for a long time. The idea is to keep the parts that have to move relatively when the packer is released free of debris so that the packer components can actually allow for the removal of the packer. Some of these designs are U.S. Pat. Nos. 7,604,048; 6,302,217 and 2,228,242. U.S. Publication 2007/0267196 uses a magnetic plug that can also be a basket that goes into a packer seal bore and when later pulled out captures debris accumulated above a long set packer before the packer is released. None of these designs are intended to capture the debris and prevent it from advancing downhole. These designs deal with debris already in the wellbore as opposed to portions of the sealing element breaking off in service.
The present invention seeks to minimize the formation of debris from portions of the sealing element coming apart without inhibiting the performance of the sealing element as a barrier. Additionally if any debris is formed the debris is also retained in a basket supported by the plug or packer. The basket is preferably closely mounted to the packer sealing element and supported by the packer mandrel. The support rod can have a breakaway connection if the basket gets stuck to allow the plug to be removed. A fishing neck can be associated with the breakaway to facilitate subsequent fishing operations for the basket. Optionally the basket or rod can have an acceleration actuated break so that if the basket breaks loose from the packer the brake will prevent the basket from falling a substantial distance. Another option can be a travel stop on the setting mechanism that will limit the rubber pressure during the setting with an eye toward reducing the tendency to create debris due to the setting and subsequent differential pressure loading of the plug. Those and other features of the present invention will be more readily apparent to those skilled in the art from a review of the detailed description and the associated drawings while recognizing that the full scope of the invention is to be found from the appended claims.